from __future__ import with_statement
import datetime
import time
import warnings
from itertools import imap, izip, starmap
from redis.connection import ConnectionPool, UnixDomainSocketConnection
from redis.exceptions import (
    ConnectionError,
    DataError,
    RedisError,
    ResponseError,
    WatchError,
)

def list_or_args(keys, args):
    # returns a single list combining keys and args
    try:
        i = iter(keys)
        # a string can be iterated, but indicates
        # keys wasn't passed as a list
        if isinstance(keys, basestring):
            keys = [keys]
    except TypeError:
        keys = [keys]
    if args:
        keys.extend(args)
    return keys

def timestamp_to_datetime(response):
    "Converts a unix timestamp to a Python datetime object"
    if not response:
        return None
    try:
        response = int(response)
    except ValueError:
        return None
    return datetime.datetime.fromtimestamp(response)

def string_keys_to_dict(key_string, callback):
    return dict.fromkeys(key_string.split(), callback)

def dict_merge(*dicts):
    merged = {}
    [merged.update(d) for d in dicts]
    return merged

def parse_info(response):
    "Parse the result of Redis's INFO command into a Python dict"
    info = {}
    def get_value(value):
        if ',' not in value:
            return value
        sub_dict = {}
        for item in value.split(','):
            k, v = item.rsplit('=', 1)
            try:
                sub_dict[k] = int(v)
            except ValueError:
                sub_dict[k] = v
        return sub_dict
    for line in response.splitlines():
        if line and not line.startswith('#'):
            key, value = line.split(':')
            try:
                if '.' in value:
                    info[key] = float(value)
                else:
                    info[key] = int(value)
            except ValueError:
                info[key] = get_value(value)
    return info

def pairs_to_dict(response):
    "Create a dict given a list of key/value pairs"
    it = iter(response)
    return dict(izip(it, it))

def zset_score_pairs(response, **options):
    """
    If withscores is specified in the options, return the response as
    a list of (value, score) pairs
    """
    if not response or not options['withscores']:
        return response
    score_cast_func = options.get('score_cast_func', float)
    it = iter(response)
    return zip(it, imap(score_cast_func, it))

def int_or_none(response):
    if response is None:
        return None
    return int(response)

def float_or_none(response):
    if response is None:
        return None
    return float(response)

def parse_config(response, **options):
    # this is stupid, but don't have a better option right now
    if options['parse'] == 'GET':
        return response and pairs_to_dict(response) or {}
    return response == 'OK'

class Redis(object):
    """
    Implementation of the Redis protocol.

    This abstract class provides a Python interface to all Redis commands
    and an implementation of the Redis protocol.

    Connection and Pipeline derive from this, implementing how
    the commands are sent and received to the Redis server
    """
    RESPONSE_CALLBACKS = dict_merge(
        string_keys_to_dict(
            'AUTH DEL EXISTS EXPIRE EXPIREAT HDEL HEXISTS HMSET MOVE MSETNX '
            'PERSIST RENAMENX SADD SISMEMBER SMOVE SETEX SETNX SREM ZADD ZREM',
            bool
            ),
        string_keys_to_dict(
            'DECRBY GETBIT HLEN INCRBY LINSERT LLEN LPUSHX RPUSHX SCARD '
            'SDIFFSTORE SETBIT SETRANGE SINTERSTORE STRLEN SUNIONSTORE ZCARD '
            'ZREMRANGEBYRANK ZREMRANGEBYSCORE',
            int
            ),
        string_keys_to_dict(
            # these return OK, or int if redis-server is >=1.3.4
            'LPUSH RPUSH',
            lambda r: isinstance(r, long) and r or r == 'OK'
            ),
        string_keys_to_dict('ZSCORE ZINCRBY', float_or_none),
        string_keys_to_dict(
            'FLUSHALL FLUSHDB LSET LTRIM MSET RENAME '
            'SAVE SELECT SET SHUTDOWN SLAVEOF WATCH UNWATCH',
            lambda r: r == 'OK'
            ),
        string_keys_to_dict('BLPOP BRPOP', lambda r: r and tuple(r) or None),
        string_keys_to_dict('SDIFF SINTER SMEMBERS SUNION',
            lambda r: r and set(r) or set()
            ),
        string_keys_to_dict('ZRANGE ZRANGEBYSCORE ZREVRANGE ZREVRANGEBYSCORE',
            zset_score_pairs
            ),
        string_keys_to_dict('ZRANK ZREVRANK', int_or_none),
        {
            'BGREWRITEAOF': lambda r: \
                r == 'Background rewriting of AOF file started',
            'BGSAVE': lambda r: r == 'Background saving started',
            'BRPOPLPUSH': lambda r: r and r or None,
            'CONFIG': parse_config,
            'HGETALL': lambda r: r and pairs_to_dict(r) or {},
            'INFO': parse_info,
            'LASTSAVE': timestamp_to_datetime,
            'PING': lambda r: r == 'PONG',
            'RANDOMKEY': lambda r: r and r or None,
            'TTL': lambda r: r != -1 and r or None,
        }
        )

    def __init__(self, host='localhost', port=6379,
                 db=0, password=None, socket_timeout=None,
                 connection_pool=None,
                 charset='utf-8', errors='strict', unix_socket_path=None):
        if not connection_pool:
            kwargs = {
                'db': db,
                'password': password,
                'socket_timeout': socket_timeout,
                'encoding': charset,
                'encoding_errors': errors
                }
            # based on input, setup appropriate connection args
            if unix_socket_path:
                kwargs.update({
                    'path': unix_socket_path,
                    'connection_class': UnixDomainSocketConnection
                })
            else:
                kwargs.update({
                    'host': host,
                    'port': port
                })
            connection_pool = ConnectionPool(**kwargs)
        self.connection_pool = connection_pool

        self.response_callbacks = self.__class__.RESPONSE_CALLBACKS.copy()

    def set_response_callback(self, command, callback):
        "Set a custom Response Callback"
        self.response_callbacks[command] = callback

    def pipeline(self, transaction=True, shard_hint=None):
        """
        Return a new pipeline object that can queue multiple commands for
        later execution. transaction indicates whether all commands
        should be executed atomically. Apart from making a group of operations
        atomic, pipelines are useful for reducing the back-and-forth overhead
        between the client and server.
        """
        return Pipeline(
            self.connection_pool,
            self.response_callbacks,
            transaction,
            shard_hint)

    def transaction(self, func, *watches, **kwargs):
        """
        Convenience method for executing the callable func as a transaction
        while watching all keys specified in watches. The 'func' callable
        should expect a single arguement which is a Pipeline object.
        """
        shard_hint = kwargs.pop('shard_hint', None)
        with self.pipeline(True, shard_hint) as pipe:
            while 1:
                try:
                    pipe.watch(*watches)
                    func(pipe)
                    return pipe.execute()
                except WatchError:
                    continue

    def lock(self, name, timeout=None, sleep=0.1):
        """
        Return a new Lock object using key name that mimics
        the behavior of threading.Lock.

        If specified, timeout indicates a maximum life for the lock.
        By default, it will remain locked until release() is called.

        sleep indicates the amount of time to sleep per loop iteration
        when the lock is in blocking mode and another client is currently
        holding the lock.
        """
        return Lock(self, name, timeout=timeout, sleep=sleep)

    def pubsub(self, shard_hint=None):
        """
        Return a Publish/Subscribe object. With this object, you can
        subscribe to channels and listen for messages that get published to
        them.
        """
        return PubSub(self.connection_pool, shard_hint)

    #### COMMAND EXECUTION AND PROTOCOL PARSING ####
    def execute_command(self, *args, **options):
        "Execute a command and return a parsed response"
        pool = self.connection_pool
        command_name = args[0]
        connection = pool.get_connection(command_name, **options)
        try:
            connection.send_command(*args)
            return self.parse_response(connection, command_name, **options)
        except ConnectionError:
            connection.disconnect()
            connection.send_command(*args)
            return self.parse_response(connection, command_name, **options)
        finally:
            pool.release(connection)

    def parse_response(self, connection, command_name, **options):
        "Parses a response from the Redis server"
        response = connection.read_response()
        if command_name in self.response_callbacks:
            return self.response_callbacks[command_name](response, **options)
        return response

    #### SERVER INFORMATION ####
    def bgrewriteaof(self):
        "Tell the Redis server to rewrite the AOF file from data in memory."
        return self.execute_command('BGREWRITEAOF')

    def bgsave(self):
        """
        Tell the Redis server to save its data to disk.  Unlike save(),
        this method is asynchronous and returns immediately.
        """
        return self.execute_command('BGSAVE')

    def config_get(self, pattern="*"):
        "Return a dictionary of configuration based on the pattern"
        return self.execute_command('CONFIG', 'GET', pattern, parse='GET')

    def config_set(self, name, value):
        "Set config item name with value"
        return self.execute_command('CONFIG', 'SET', name, value, parse='SET')

    def dbsize(self):
        "Returns the number of keys in the current database"
        return self.execute_command('DBSIZE')

    def delete(self, *names):
        "Delete one or more keys specified by names"
        return self.execute_command('DEL', *names)
    __delitem__ = delete

    def flushall(self):
        "Delete all keys in all databases on the current host"
        return self.execute_command('FLUSHALL')

    def flushdb(self):
        "Delete all keys in the current database"
        return self.execute_command('FLUSHDB')

    def info(self):
        "Returns a dictionary containing information about the Redis server"
        return self.execute_command('INFO')

    def lastsave(self):
        """
        Return a Python datetime object representing the last time the
        Redis database was saved to disk
        """
        return self.execute_command('LASTSAVE')

    def ping(self):
        "Ping the Redis server"
        return self.execute_command('PING')

    def save(self):
        """
        Tell the Redis server to save its data to disk,
        blocking until the save is complete
        """
        return self.execute_command('SAVE')

    def shutdown(self):
        "Shutdown the server"
        try:
            self.execute_command('SHUTDOWN')
        except ConnectionError:
            # a ConnectionError here is expected
            return
        raise RedisError("SHUTDOWN seems to have failed.")

    def slaveof(self, host=None, port=None):
        """
        Set the server to be a replicated slave of the instance identified
        by the host and port. If called without arguements, the
        instance is promoted to a master instead.
        """
        if host is None and port is None:
            return self.execute_command("SLAVEOF", "NO", "ONE")
        return self.execute_command("SLAVEOF", host, port)

    #### BASIC KEY COMMANDS ####
    def append(self, key, value):
        """
        Appends the string value to the value at key. If key
        doesn't already exist, create it with a value of value.
        Returns the new length of the value at key.
        """
        return self.execute_command('APPEND', key, value)

    def decr(self, name, amount=1):
        """
        Decrements the value of key by amount.  If no key exists,
        the value will be initialized as 0 - amount
        """
        return self.execute_command('DECRBY', name, amount)

    def exists(self, name):
        "Returns a boolean indicating whether key name exists"
        return self.execute_command('EXISTS', name)
    __contains__ = exists

    def expire(self, name, time):
        "Set an expire flag on key name for time seconds"
        return self.execute_command('EXPIRE', name, time)

    def expireat(self, name, when):
        """
        Set an expire flag on key name. when can be represented
        as an integer indicating unix time or a Python datetime object.
        """
        if isinstance(when, datetime.datetime):
            when = int(time.mktime(when.timetuple()))
        return self.execute_command('EXPIREAT', name, when)

    def get(self, name):
        """
        Return the value at key name, or None if the key doesn't exist
        """
        return self.execute_command('GET', name)

    def __getitem__(self, name):
        """
        Return the value at key name, raises a KeyError if the key
        doesn't exist.
        """
        value = self.get(name)
        if value:
            return value
        raise KeyError(name)

    def getbit(self, name, offset):
        "Returns a boolean indicating the value of offset in name"
        return self.execute_command('GETBIT', name, offset)

    def getset(self, name, value):
        """
        Set the value at key name to value if key doesn't exist
        Return the value at key name atomically
        """
        return self.execute_command('GETSET', name, value)

    def incr(self, name, amount=1):
        """
        Increments the value of key by amount.  If no key exists,
        the value will be initialized as amount
        """
        return self.execute_command('INCRBY', name, amount)

    def keys(self, pattern='*'):
        "Returns a list of keys matching pattern"
        return self.execute_command('KEYS', pattern)

    def mget(self, keys, *args):
        """
        Returns a list of values ordered identically to keys
        """
        keys = list_or_args(keys, args)
        return self.execute_command('MGET', *keys)

    def mset(self, mapping):
        "Sets each key in the mapping dict to its corresponding value"
        items = []
        for pair in mapping.iteritems():
            items.extend(pair)
        return self.execute_command('MSET', *items)

    def msetnx(self, mapping):
        """
        Sets each key in the mapping dict to its corresponding value if
        none of the keys are already set
        """
        items = []
        for pair in mapping.iteritems():
            items.extend(pair)
        return self.execute_command('MSETNX', *items)

    def move(self, name, db):
        "Moves the key name to a different Redis database db"
        return self.execute_command('MOVE', name, db)

    def persist(self, name):
        "Removes an expiration on name"
        return self.execute_command('PERSIST', name)

    def randomkey(self):
        "Returns the name of a random key"
        return self.execute_command('RANDOMKEY')

    def rename(self, src, dst):
        """
        Rename key src to dst
        """
        return self.execute_command('RENAME', src, dst)

    def renamenx(self, src, dst):
        "Rename key src to dst if dst doesn't already exist"
        return self.execute_command('RENAMENX', src, dst)

    def set(self, name, value):
        "Set the value at key name to value"
        return self.execute_command('SET', name, value)
    __setitem__ = set

    def setbit(self, name, offset, value):
        """
        Flag the offset in name as value. Returns a boolean
        indicating the previous value of offset.
        """
        value = value and 1 or 0
        return self.execute_command('SETBIT', name, offset, value)

    def setex(self, name, value, time):
        """
        Set the value of key name to value
        that expires in time seconds
        """
        return self.execute_command('SETEX', name, time, value)

    def setnx(self, name, value):
        "Set the value of key name to value if key doesn't exist"
        return self.execute_command('SETNX', name, value)

    def setrange(self, name, offset, value):
        """
        Overwrite bytes in the value of name starting at offset with
        value. If offset plus the length of value exceeds the
        length of the original value, the new value will be larger than before.
        If offset exceeds the length of the original value, null bytes
        will be used to pad between the end of the previous value and the start
        of what's being injected.

        Returns the length of the new string.
        """
        return self.execute_command('SETRANGE', name, offset, value)

    def strlen(self, name):
        "Return the number of bytes stored in the value of name"
        return self.execute_command('STRLEN', name)

    def substr(self, name, start, end=-1):
        """
        Return a substring of the string at key name. start and end
        are 0-based integers specifying the portion of the string to return.
        """
        return self.execute_command('SUBSTR', name, start, end)

    def ttl(self, name):
        "Returns the number of seconds until the key name will expire"
        return self.execute_command('TTL', name)

    def type(self, name):
        "Returns the type of key name"
        return self.execute_command('TYPE', name)

    def watch(self, *names):
        """
        Watches the values at keys names, or None if the key doesn't exist
        """
        warnings.warn(DeprecationWarning('Call WATCH from a Pipeline object'))

    def unwatch(self):
        """
        Unwatches the value at key name, or None of the key doesn't exist
        """
        warnings.warn(DeprecationWarning('Call UNWATCH from a Pipeline object'))

    #### LIST COMMANDS ####
    def blpop(self, keys, timeout=0):
        """
        LPOP a value off of the first non-empty list
        named in the keys list.

        If none of the lists in keys has a value to LPOP, then block
        for timeout seconds, or until a value gets pushed on to one
        of the lists.

        If timeout is 0, then block indefinitely.
        """
        if timeout is None:
            timeout = 0
        if isinstance(keys, basestring):
            keys = [keys]
        else:
            keys = list(keys)
        keys.append(timeout)
        return self.execute_command('BLPOP', *keys)

    def brpop(self, keys, timeout=0):
        """
        RPOP a value off of the first non-empty list
        named in the keys list.

        If none of the lists in keys has a value to LPOP, then block
        for timeout seconds, or until a value gets pushed on to one
        of the lists.

        If timeout is 0, then block indefinitely.
        """
        if timeout is None:
            timeout = 0
        if isinstance(keys, basestring):
            keys = [keys]
        else:
            keys = list(keys)
        keys.append(timeout)
        return self.execute_command('BRPOP', *keys)

    def brpoplpush(self, src, dst, timeout=0):
        """
        Pop a value off the tail of src, push it on the head of dst
        and then return it.

        This command blocks until a value is in src or until timeout
        seconds elapse, whichever is first. A timeout value of 0 blocks
        forever.
        """
        if timeout is None:
            timeout = 0
        return self.execute_command('BRPOPLPUSH', src, dst, timeout)

    def lindex(self, name, index):
        """
        Return the item from list name at position index

        Negative indexes are supported and will return an item at the
        end of the list
        """
        return self.execute_command('LINDEX', name, index)

    def linsert(self, name, where, refvalue, value):
        """
        Insert value in list name either immediately before or after
        [where] refvalue

        Returns the new length of the list on success or -1 if refvalue
        is not in the list.
        """
        return self.execute_command('LINSERT', name, where, refvalue, value)

    def llen(self, name):
        "Return the length of the list name"
        return self.execute_command('LLEN', name)

    def lpop(self, name):
        "Remove and return the first item of the list name"
        return self.execute_command('LPOP', name)

    def lpush(self, name, *values):
        "Push values onto the head of the list name"
        return self.execute_command('LPUSH', name, *values)

    def lpushx(self, name, value):
        "Push value onto the head of the list name if name exists"
        return self.execute_command('LPUSHX', name, value)

    def lrange(self, name, start, end):
        """
        Return a slice of the list name between
        position start and end

        start and end can be negative numbers just like
        Python slicing notation
        """
        return self.execute_command('LRANGE', name, start, end)

    def lrem(self, name, value, num=0):
        """
        Remove the first num occurrences of value from list name

        If num is 0, then all occurrences will be removed
        """
        return self.execute_command('LREM', name, num, value)

    def lset(self, name, index, value):
        "Set position of list name to value"
        return self.execute_command('LSET', name, index, value)

    def ltrim(self, name, start, end):
        """
        Trim the list name, removing all values not within the slice
        between start and end

        start and end can be negative numbers just like
        Python slicing notation
        """
        return self.execute_command('LTRIM', name, start, end)

    def rpop(self, name):
        "Remove and return the last item of the list name"
        return self.execute_command('RPOP', name)

    def rpoplpush(self, src, dst):
        """
        RPOP a value off of the src list and atomically LPUSH it
        on to the dst list.  Returns the value.
        """
        return self.execute_command('RPOPLPUSH', src, dst)

    def rpush(self, name, *values):
        "Push values onto the tail of the list name"
        return self.execute_command('RPUSH', name, *values)

    def rpushx(self, name, value):
        "Push value onto the tail of the list name if name exists"
        return self.execute_command('RPUSHX', name, value)

    def sort(self, name, start=None, num=None, by=None, get=None,
             desc=False, alpha=False, store=None):
        """
        Sort and return the list, set or sorted set at name.

        start and num allow for paging through the sorted data

        by allows using an external key to weight and sort the items.
            Use an "*" to indicate where in the key the item value is located

        get allows for returning items from external keys rather than the
            sorted data itself.  Use an "*" to indicate where int he key
            the item value is located

        desc allows for reversing the sort

        alpha allows for sorting lexicographically rather than numerically

        store allows for storing the result of the sort into
            the key store
        """
        if (start is not None and num is None) or \
                (num is not None and start is None):
            raise RedisError("start and num must both be specified")

        pieces = [name]
        if by is not None:
            pieces.append('BY')
            pieces.append(by)
        if start is not None and num is not None:
            pieces.append('LIMIT')
            pieces.append(start)
            pieces.append(num)
        if get is not None:
            # If get is a string assume we want to get a single value.
            # Otherwise assume it's an interable and we want to get multiple
            # values. We can't just iterate blindly because strings are
            # iterable.
            if isinstance(get, basestring):
                pieces.append('GET')
                pieces.append(get)
            else:
                for g in get:
                    pieces.append('GET')
                    pieces.append(g)
        if desc:
            pieces.append('DESC')
        if alpha:
            pieces.append('ALPHA')
        if store is not None:
            pieces.append('STORE')
            pieces.append(store)
        return self.execute_command('SORT', *pieces)


    #### SET COMMANDS ####
    def sadd(self, name, *values):
        "Add value(s) to set name"
        return self.execute_command('SADD', name, *values)

    def scard(self, name):
        "Return the number of elements in set name"
        return self.execute_command('SCARD', name)

    def sdiff(self, keys, *args):
        "Return the difference of sets specified by keys"
        keys = list_or_args(keys, args)
        return self.execute_command('SDIFF', *keys)

    def sdiffstore(self, dest, keys, *args):
        """
        Store the difference of sets specified by keys into a new
        set named dest.  Returns the number of keys in the new set.
        """
        keys = list_or_args(keys, args)
        return self.execute_command('SDIFFSTORE', dest, *keys)

    def sinter(self, keys, *args):
        "Return the intersection of sets specified by keys"
        keys = list_or_args(keys, args)
        return self.execute_command('SINTER', *keys)

    def sinterstore(self, dest, keys, *args):
        """
        Store the intersection of sets specified by keys into a new
        set named dest.  Returns the number of keys in the new set.
        """
        keys = list_or_args(keys, args)
        return self.execute_command('SINTERSTORE', dest, *keys)

    def sismember(self, name, value):
        "Return a boolean indicating if value is a member of set name"
        return self.execute_command('SISMEMBER', name, value)

    def smembers(self, name):
        "Return all members of the set name"
        return self.execute_command('SMEMBERS', name)

    def smove(self, src, dst, value):
        "Move value from set src to set dst atomically"
        return self.execute_command('SMOVE', src, dst, value)

    def spop(self, name):
        "Remove and return a random member of set name"
        return self.execute_command('SPOP', name)

    def srandmember(self, name):
        "Return a random member of set name"
        return self.execute_command('SRANDMEMBER', name)

    def srem(self, name, *values):
        "Remove values from set name"
        return self.execute_command('SREM', name, *values)

    def sunion(self, keys, *args):
        "Return the union of sets specifiued by keys"
        keys = list_or_args(keys, args)
        return self.execute_command('SUNION', *keys)

    def sunionstore(self, dest, keys, *args):
        """
        Store the union of sets specified by keys into a new
        set named dest.  Returns the number of keys in the new set.
        """
        keys = list_or_args(keys, args)
        return self.execute_command('SUNIONSTORE', dest, *keys)


    #### SORTED SET COMMANDS ####
    def zadd(self, name, value=None, score=None, **pairs):
        """
        For each kwarg in pairs, add that item and it's score to the
        sorted set name.

        The value and score arguments are deprecated.
        """
        all_pairs = []
        if value is not None or score is not None:
            if value is None or score is None:
                raise RedisError("Both 'value' and 'score' must be specified " \
                                 "to ZADD")
            warnings.warn(DeprecationWarning(
                "Passing 'value' and 'score' has been deprecated. " \
                "Please pass via kwargs instead."))
            all_pairs.append(score)
            all_pairs.append(value)
        for pair in pairs.iteritems():
            all_pairs.append(pair[1])
            all_pairs.append(pair[0])
        return self.execute_command('ZADD', name, *all_pairs)

    def zcard(self, name):
        "Return the number of elements in the sorted set name"
        return self.execute_command('ZCARD', name)

    def zcount(self, name, min, max):
        return self.execute_command('ZCOUNT', name, min, max)

    def zincrby(self, name, value, amount=1):
        "Increment the score of value in sorted set name by amount"
        return self.execute_command('ZINCRBY', name, amount, value)

    def zinterstore(self, dest, keys, aggregate=None):
        """
        Intersect multiple sorted sets specified by keys into
        a new sorted set, dest. Scores in the destination will be
        aggregated based on the aggregate, or SUM if none is provided.
        """
        return self._zaggregate('ZINTERSTORE', dest, keys, aggregate)

    def zrange(self, name, start, end, desc=False, withscores=False,
               score_cast_func=float):
        """
        Return a range of values from sorted set name between
        start and end sorted in ascending order.

        start and end can be negative, indicating the end of the range.

        desc a boolean indicating whether to sort the results descendingly

        withscores indicates to return the scores along with the values.
        The return type is a list of (value, score) pairs

        score_cast_func a callable used to cast the score return value
        """
        if desc:
            return self.zrevrange(name, start, end, withscores)
        pieces = ['ZRANGE', name, start, end]
        if withscores:
            pieces.append('withscores')
        options = {'withscores': withscores, 'score_cast_func': score_cast_func}
        return self.execute_command(*pieces, **options)

    def zrangebyscore(self, name, min, max,
            start=None, num=None, withscores=False, score_cast_func=float):
        """
        Return a range of values from the sorted set name with scores
        between min and max.

        If start and num are specified, then return a slice
        of the range.

        withscores indicates to return the scores along with the values.
        The return type is a list of (value, score) pairs

        score_cast_func a callable used to cast the score return value
        """
        if (start is not None and num is None) or \
                (num is not None and start is None):
            raise RedisError("start and num must both be specified")
        pieces = ['ZRANGEBYSCORE', name, min, max]
        if start is not None and num is not None:
            pieces.extend(['LIMIT', start, num])
        if withscores:
            pieces.append('withscores')
        options = {'withscores': withscores, 'score_cast_func': score_cast_func}
        return self.execute_command(*pieces, **options)

    def zrank(self, name, value):
        """
        Returns a 0-based value indicating the rank of value in sorted set
        name
        """
        return self.execute_command('ZRANK', name, value)

    def zrem(self, name, *values):
        "Remove member values from sorted set name"
        return self.execute_command('ZREM', name, *values)

    def zremrangebyrank(self, name, min, max):
        """
        Remove all elements in the sorted set name with ranks between
        min and max. Values are 0-based, ordered from smallest score
        to largest. Values can be negative indicating the highest scores.
        Returns the number of elements removed
        """
        return self.execute_command('ZREMRANGEBYRANK', name, min, max)

    def zremrangebyscore(self, name, min, max):
        """
        Remove all elements in the sorted set name with scores
        between min and max. Returns the number of elements removed.
        """
        return self.execute_command('ZREMRANGEBYSCORE', name, min, max)

    def zrevrange(self, name, start, num, withscores=False,
                  score_cast_func=float):
        """
        Return a range of values from sorted set name between
        start and num sorted in descending order.

        start and num can be negative, indicating the end of the range.

        withscores indicates to return the scores along with the values
        The return type is a list of (value, score) pairs

        score_cast_func a callable used to cast the score return value
        """
        pieces = ['ZREVRANGE', name, start, num]
        if withscores:
            pieces.append('withscores')
        options = {'withscores': withscores, 'score_cast_func': score_cast_func}
        return self.execute_command(*pieces, **options)

    def zrevrangebyscore(self, name, max, min,
            start=None, num=None, withscores=False, score_cast_func=float):
        """
        Return a range of values from the sorted set name with scores
        between min and max in descending order.

        If start and num are specified, then return a slice
        of the range.

        withscores indicates to return the scores along with the values.
        The return type is a list of (value, score) pairs

        score_cast_func a callable used to cast the score return value
        """
        if (start is not None and num is None) or \
                (num is not None and start is None):
            raise RedisError("start and num must both be specified")
        pieces = ['ZREVRANGEBYSCORE', name, max, min]
        if start is not None and num is not None:
            pieces.extend(['LIMIT', start, num])
        if withscores:
            pieces.append('withscores')
        options = {'withscores': withscores, 'score_cast_func': score_cast_func}
        return self.execute_command(*pieces, **options)

    def zrevrank(self, name, value):
        """
        Returns a 0-based value indicating the descending rank of
        value in sorted set name
        """
        return self.execute_command('ZREVRANK', name, value)

    def zscore(self, name, value):
        "Return the score of element value in sorted set name"
        return self.execute_command('ZSCORE', name, value)

    def zunionstore(self, dest, keys, aggregate=None):
        """
        Union multiple sorted sets specified by keys into
        a new sorted set, dest. Scores in the destination will be
        aggregated based on the aggregate, or SUM if none is provided.
        """
        return self._zaggregate('ZUNIONSTORE', dest, keys, aggregate)

    def _zaggregate(self, command, dest, keys, aggregate=None):
        pieces = [command, dest, len(keys)]
        if isinstance(keys, dict):
            keys, weights = keys.keys(), keys.values()
        else:
            weights = None
        pieces.extend(keys)
        if weights:
            pieces.append('WEIGHTS')
            pieces.extend(weights)
        if aggregate:
            pieces.append('AGGREGATE')
            pieces.append(aggregate)
        return self.execute_command(*pieces)

    #### HASH COMMANDS ####
    def hdel(self, name, *keys):
        "Delete keys from hash name"
        return self.execute_command('HDEL', name, *keys)

    def hexists(self, name, key):
        "Returns a boolean indicating if key exists within hash name"
        return self.execute_command('HEXISTS', name, key)

    def hget(self, name, key):
        "Return the value of key within the hash name"
        return self.execute_command('HGET', name, key)

    def hgetall(self, name):
        "Return a Python dict of the hash's name/value pairs"
        return self.execute_command('HGETALL', name)

    def hincrby(self, name, key, amount=1):
        "Increment the value of key in hash name by amount"
        return self.execute_command('HINCRBY', name, key, amount)

    def hkeys(self, name):
        "Return the list of keys within hash name"
        return self.execute_command('HKEYS', name)

    def hlen(self, name):
        "Return the number of elements in hash name"
        return self.execute_command('HLEN', name)

    def hset(self, name, key, value):
        """
        Set key to value within hash name
        Returns 1 if HSET created a new field, otherwise 0
        """
        return self.execute_command('HSET', name, key, value)

    def hsetnx(self, name, key, value):
        """
        Set key to value within hash name if key does not
        exist.  Returns 1 if HSETNX created a field, otherwise 0.
        """
        return self.execute_command("HSETNX", name, key, value)

    def hmset(self, name, mapping):
        """
        Sets each key in the mapping dict to its corresponding value
        in the hash name
        """
        if not mapping:
            raise DataError("'hmset' with 'mapping' of length 0")
        items = []
        for pair in mapping.iteritems():
            items.extend(pair)
        return self.execute_command('HMSET', name, *items)

    def hmget(self, name, keys):
        "Returns a list of values ordered identically to keys"
        return self.execute_command('HMGET', name, *keys)

    def hvals(self, name):
        "Return the list of values within hash name"
        return self.execute_command('HVALS', name)

    def publish(self, channel, message):
        """
        Publish message on channel.
        Returns the number of subscribers the message was delivered to.
        """
        return self.execute_command('PUBLISH', channel, message)


class PubSub(object):
    """
    PubSub provides publish, subscribe and listen support to Redis channels.

    After subscribing to one or more channels, the listen() method will block
    until a message arrives on one of the subscribed channels. That message
    will be returned and it's safe to start listening again.
    """
    def __init__(self, connection_pool, shard_hint=None):
        self.connection_pool = connection_pool
        self.shard_hint = shard_hint
        self.connection = None
        self.channels = set()
        self.patterns = set()
        self.subscription_count = 0
        self.subscribe_commands = set(
            ('subscribe', 'psubscribe', 'unsubscribe', 'punsubscribe')
            )

    def execute_command(self, *args, **kwargs):
        "Execute a publish/subscribe command"
        if self.connection is None:
            self.connection = self.connection_pool.get_connection(
                'pubsub',
                self.shard_hint
                )
        connection = self.connection
        try:
            connection.send_command(*args)
            return self.parse_response()
        except ConnectionError:
            connection.disconnect()
            # resubscribe to all channels and patterns before
            # resending the current command
            for channel in self.channels:
                self.subscribe(channel)
            for pattern in self.patterns:
                self.psubscribe(pattern)
            connection.send_command(*args)
            return self.parse_response()

    def parse_response(self):
        "Parse the response from a publish/subscribe command"
        response = self.connection.read_response()
        if response[0] in self.subscribe_commands:
            self.subscription_count = response[2]
            # if we've just unsubscribed from the remaining channels,
            # release the connection back to the pool
            if not self.subscription_count:
                self.connection_pool.release(self.connection)
                self.connection = None
        return response

    def psubscribe(self, patterns):
        "Subscribe to all channels matching any pattern in patterns"
        if isinstance(patterns, basestring):
            patterns = [patterns]
        for pattern in patterns:
            self.patterns.add(pattern)
        return self.execute_command('PSUBSCRIBE', *patterns)

    def punsubscribe(self, patterns=[]):
        """
        Unsubscribe from any channel matching any pattern in patterns.
        If empty, unsubscribe from all channels.
        """
        if isinstance(patterns, basestring):
            patterns = [patterns]
        for pattern in patterns:
            try:
                self.patterns.remove(pattern)
            except KeyError:
                pass
        return self.execute_command('PUNSUBSCRIBE', *patterns)

    def subscribe(self, channels):
        "Subscribe to channels, waiting for messages to be published"
        if isinstance(channels, basestring):
            channels = [channels]
        for channel in channels:
            self.channels.add(channel)
        return self.execute_command('SUBSCRIBE', *channels)

    def unsubscribe(self, channels=[]):
        """
        Unsubscribe from channels. If empty, unsubscribe
        from all channels
        """
        if isinstance(channels, basestring):
            channels = [channels]
        for channel in channels:
            try:
                self.channels.remove(channel)
            except KeyError:
                pass
        return self.execute_command('UNSUBSCRIBE', *channels)

    def listen(self):
        "Listen for messages on channels this client has been subscribed to"
        while self.subscription_count:
            r = self.parse_response()
            if r[0] == 'pmessage':
                msg = {
                    'type': r[0],
                    'pattern': r[1],
                    'channel': r[2],
                    'data': r[3]
                }
            else:
                msg = {
                    'type': r[0],
                    'pattern': None,
                    'channel': r[1],
                    'data': r[2]
                }
            yield msg


class Pipeline(Redis):
    """
    Pipelines provide a way to transmit multiple commands to the Redis server
    in one transmission.  This is convenient for batch processing, such as
    saving all the values in a list to Redis.

    All commands executed within a pipeline are wrapped with MULTI and EXEC
    calls. This guarantees all commands executed in the pipeline will be
    executed atomically.

    Any command raising an exception does *not* halt the execution of
    subsequent commands in the pipeline. Instead, the exception is caught
    and its instance is placed into the response list returned by execute().
    Code iterating over the response list should be able to deal with an
    instance of an exception as a potential value. In general, these will be
    ResponseError exceptions, such as those raised when issuing a command
    on a key of a different datatype.
    """

    UNWATCH_COMMANDS = set(('DISCARD', 'EXEC', 'UNWATCH'))

    def __init__(self, connection_pool, response_callbacks, transaction,
                 shard_hint):
        self.connection_pool = connection_pool
        self.connection = None
        self.response_callbacks = response_callbacks
        self.transaction = transaction
        self.shard_hint = shard_hint

        self.watching = False
        self.reset()

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        self.reset()

    def reset(self):
        self.command_stack = []
        # make sure to reset the connection state in the event that we were
        # watching something
        if self.watching and self.connection:
            try:
                # call this manually since our unwatch or
                # immediate_execute_command methods can call reset()
                self.connection.send_command('UNWATCH')
                self.connection.read_response()
            except ConnectionError:
                # disconnect will also remove any previous WATCHes
                self.connection.disconnect()
        # clean up the other instance attributes
        self.watching = False
        self.explicit_transaction = False
        # we can safely return the connection to the pool here since we're
        # sure we're no longer WATCHing anything
        if self.connection:
            self.connection_pool.release(self.connection)
            self.connection = None

    def multi(self):
        """
        Start a transactional block of the pipeline after WATCH commands
        are issued. End the transactional block with execute.
        """
        if self.explicit_transaction:
            raise RedisError('Cannot issue nested calls to MULTI')
        if self.command_stack:
            raise RedisError('Commands without an initial WATCH have already '
                             'been issued')
        self.explicit_transaction = True

    def execute_command(self, *args, **kwargs):
        if (self.watching or args[0] == 'WATCH') and \
                not self.explicit_transaction:
            return self.immediate_execute_command(*args, **kwargs)
        return self.pipeline_execute_command(*args, **kwargs)

    def immediate_execute_command(self, *args, **options):
        """
        Execute a command immediately, but don't auto-retry on a
        ConnectionError if we're already WATCHing a variable. Used when
        issuing WATCH or subsequent commands retrieving their values but before
        MULTI is called.
        """
        command_name = args[0]
        conn = self.connection
        # if this is the first call, we need a connection
        if not conn:
            conn = self.connection_pool.get_connection(command_name,
                                                       self.shard_hint)
            self.connection = conn
        try:
            conn.send_command(*args)
            return self.parse_response(conn, command_name, **options)
        except ConnectionError:
            conn.disconnect()
            # if we're not already watching, we can safely retry the command
            # assuming it was a connection timeout
            if not self.watching:
                conn.send_command(*args)
                return self.parse_response(conn, command_name, **options)
            self.reset()
            raise

    def pipeline_execute_command(self, *args, **options):
        """
        Stage a command to be executed when execute() is next called

        Returns the current Pipeline object back so commands can be
        chained together, such as:

        pipe = pipe.set('foo', 'bar').incr('baz').decr('bang')

        At some other point, you can then run: pipe.execute(),
        which will execute all commands queued in the pipe.
        """
        self.command_stack.append((args, options))
        return self

    def _execute_transaction(self, connection, commands):
        all_cmds = ''.join(starmap(connection.pack_command,
                                   [args for args, options in commands]))
        connection.send_packed_command(all_cmds)
        # we don't care about the multi/exec any longer
        commands = commands[1:-1]
        # parse off the response for MULTI and all commands prior to EXEC.
        # the only data we care about is the response the EXEC
        # which is the last command
        for i in range(len(commands)+1):
            self.parse_response(connection, '_')
        # parse the EXEC.
        response = self.parse_response(connection, '_')

        if response is None:
            raise WatchError("Watched variable changed.")

        if len(response) != len(commands):
            raise ResponseError("Wrong number of response items from "
                                "pipeline execution")
        # We have to run response callbacks manually
        data = []
        for r, cmd in izip(response, commands):
            if not isinstance(r, Exception):
                args, options = cmd
                command_name = args[0]
                if command_name in self.response_callbacks:
                    r = self.response_callbacks[command_name](r, **options)
            data.append(r)
        return data

    def _execute_pipeline(self, connection, commands):
        # build up all commands into a single request to increase network perf
        all_cmds = ''.join(starmap(connection.pack_command,
                                   [args for args, options in commands]))
        connection.send_packed_command(all_cmds)
        return [self.parse_response(connection, args[0], **options)
                for args, options in commands]

    def parse_response(self, connection, command_name, **options):
        result = super(Pipeline, self).parse_response(
            connection, command_name, **options)
        if command_name in self.UNWATCH_COMMANDS:
            self.watching = False
        elif command_name == 'WATCH':
            self.watching = True
        return result

    def execute(self):
        "Execute all the commands in the current pipeline"
        stack = self.command_stack
        if self.transaction or self.explicit_transaction:
            stack = [(('MULTI' ,), {})] + stack + [(('EXEC', ), {})]
            execute = self._execute_transaction
        else:
            execute = self._execute_pipeline

        conn = self.connection
        if not conn:
            conn = self.connection_pool.get_connection('MULTI', self.shard_hint)
            # assign to self.connection so reset() releases the connection
            # back to the pool after we're done
            self.connection = conn

        try:
            return execute(conn, stack)
        except ConnectionError:
            conn.disconnect()
            # if we were watching a variable, the watch is no longer valid since
            # this connection has died. raise a WatchError, which indicates
            # the user should retry his transaction. If this is more than a
            # temporary failure, the WATCH that the user next issue will fail,
            # propegating the real ConnectionError
            if self.watching:
                raise WatchError("A ConnectionError occured on while watching "
                                 "one or more keys")
            # otherwise, it's safe to retry since the transaction isn't
            # predicated on any state
            return execute(conn, stack)
        finally:
            self.reset()

    def watch(self, *names):
        """
        Watches the values at keys names
        """
        if self.explicit_transaction:
            raise RedisError('Cannot issue a WATCH after a MULTI')
        return self.execute_command('WATCH', *names)

    def unwatch(self):
        """
        Unwatches all previously specified keys
        """
        return self.watching and self.execute_command('UNWATCH') or True


class LockError(RedisError):
    "Errors thrown from the Lock"
    pass

class Lock(object):
    """
    A shared, distributed Lock. Using Redis for locking allows the Lock
    to be shared across processes and/or machines.

    It's left to the user to resolve deadlock issues and make sure
    multiple clients play nicely together.
    """

    LOCK_FOREVER = float(2**31+1) # 1 past max unix time

    def __init__(self, redis, name, timeout=None, sleep=0.1):
        """
        Create a new Lock instnace named name using the Redis client
        supplied by redis.

        timeout indicates a maximum life for the lock.
        By default, it will remain locked until release() is called.

        sleep indicates the amount of time to sleep per loop iteration
        when the lock is in blocking mode and another client is currently
        holding the lock.

        Note: If using timeout, you should make sure all the hosts
        that are running clients are within the same timezone and are using
        a network time service like ntp.
        """
        self.redis = redis
        self.name = name
        self.acquired_until = None
        self.timeout = timeout
        self.sleep = sleep
        if self.timeout and self.sleep > self.timeout:
            raise LockError("'sleep' must be less than 'timeout'")

    def __enter__(self):
        return self.acquire()

    def __exit__(self, exc_type, exc_value, traceback):
        self.release()

    def acquire(self, blocking=True):
        """
        Use Redis to hold a shared, distributed lock named name.
        Returns True once the lock is acquired.

        If blocking is False, always return immediately. If the lock
        was acquired, return True, otherwise return False.
        """
        sleep = self.sleep
        timeout = self.timeout
        while 1:
            unixtime = int(time.time())
            if timeout:
                timeout_at = unixtime + timeout
            else:
                timeout_at = Lock.LOCK_FOREVER
            timeout_at = float(timeout_at)
            if self.redis.setnx(self.name, timeout_at):
                self.acquired_until = timeout_at
                return True
            # We want blocking, but didn't acquire the lock
            # check to see if the current lock is expired
            existing = float(self.redis.get(self.name) or 1)
            if existing < unixtime:
                # the previous lock is expired, attempt to overwrite it
                existing = float(self.redis.getset(self.name, timeout_at) or 1)
                if existing < unixtime:
                    # we successfully acquired the lock
                    self.acquired_until = timeout_at
                    return True
            if not blocking:
                return False
            time.sleep(sleep)

    def release(self):
        "Releases the already acquired lock"
        if self.acquired_until is None:
            raise ValueError("Cannot release an unlocked lock")
        existing = float(self.redis.get(self.name) or 1)
        # if the lock time is in the future, delete the lock
        if existing >= self.acquired_until:
            self.redis.delete(self.name)
        self.acquired_until = None
